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Faculty Publications

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Articles 2911 - 2940 of 3294

Full-Text Articles in Engineering

Benevolent Agents, Michael N. Huhns, Abdulla Mohamed Jan 1999

Benevolent Agents, Michael N. Huhns, Abdulla Mohamed

Faculty Publications

Some agents roaming the Web these days are benevolent-for example, they may clean up stalled or failed database transactions, or share query results that may have cost substantial resources to acquire and might consume more to share. The Agent Behavior Testbed is a tool for studying the economics of agent altruism. As more agents hit the Internet, benevolence and cooperation will help with overall efficiency and productivity. The paper discusses benevolent agents on the Web.

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Networking Embedded Agents, Michael N. Huhns Jan 1999

Networking Embedded Agents, Michael N. Huhns

Faculty Publications

Most of us will soon be managing an intranet in our homes, though we might not realize it. We might also be surprised at the devices that will be networked together. Just about every electrical device now contains one or more microprocessors. Designers typically find this a cost-effective way to provide device functionality, even when much of a processor's power is unnecessary or unused. For example, my coffee maker contains a processor, even though the appliance needn't be very smart and wastes most of its CPU cycles. Nevertheless, it is cheaper to include a general-purpose microprocessor than to incorporate custom …

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Negotiating For Goods And Services, Michael N. Huhns, Anuj K. Malhotra Jan 1999

Negotiating For Goods And Services, Michael N. Huhns, Anuj K. Malhotra

Faculty Publications

Can a negotiation protocol be both fair and “envy-free” when more than two agents are involved? The authors consider how envy-free apportioning is more difficult than fair apportioning, but both can help to manage critical resources. They discuss an envy-free protocol and agent-based Web auctions.

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Integrated Computational Chemistry System For Catalysts Design, Salai Cheettu Ammal, S. Takami, M. Kubo, A. Miyamoto Jan 1999

Integrated Computational Chemistry System For Catalysts Design, Salai Cheettu Ammal, S. Takami, M. Kubo, A. Miyamoto

Faculty Publications

The understanding of valuable catalytic and adsorptive properties of heterogeneous catalysts at atomic and electronic levels is essential for the design of novel catalysts. Computer simulation studies can significantly contribute to provide a rational interpretation of the observed experimental results and suggest modification of new catalysts. Our recent work on the application of integrated computer simulation methods to investigate the structure and catalytic properties of solid surfaces including zeolites, transition metals and their oxides have been reviewed in this paper. We have emphasized the effectivity and applicability of integrated computer simulation system to solve the problems in a variety of …

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Material Balance Modification In One-Dimensional Modeling Of Porous Electrodes, Mukul Jain, John W. Weidner Jan 1999

Material Balance Modification In One-Dimensional Modeling Of Porous Electrodes, Mukul Jain, John W. Weidner

Faculty Publications

The material balance used previously in one-dimensional mathematical models of porous electrodes is invalid when there is a non-zero volume change associated with the reaction. It is shown here how the material balance should be modified either to account for a loss in volume, or to account for an inflow of electrolyte from the header into the active pores. A one-dimensional mathematical model is used to illustrate the effect of this correction on the prediction of the delivered capacity and the electrolyte concentration in a lithium/thionyl chloride primary battery.

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Correlation Of Double-Layer Capacitance With The Pore Structure Of Sol-Gel Derived Carbon Xerogels, Chuan Lin, James A. Ritter, Branko N. Popov Jan 1999

Correlation Of Double-Layer Capacitance With The Pore Structure Of Sol-Gel Derived Carbon Xerogels, Chuan Lin, James A. Ritter, Branko N. Popov

Faculty Publications

Nine different sol-gel derived carbon xerogels were prepared with different pore structures by varying the carbonization temperature (in flowing N2) and activation time (in 5% CO2 in N2). For each of these carbon xerogels, mesopore and micropore size distributions and cumulative surface areas were extracted from a density functional theory analysis. Increasing the carbonization temperature caused a decrease in the number of micropores in the 6 Å range but had little effect on the mesopore size distribution and thus mesopore cumulative surface area. Increasing the CO2 activation time caused an increase in the number …

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A Mathematical Model Of An Electrochemical Capacitor With Double-Layer And Faradaic Processes, Chuan Lin, James A. Ritter, Branko N. Popov, Ralph E. White Jan 1999

A Mathematical Model Of An Electrochemical Capacitor With Double-Layer And Faradaic Processes, Chuan Lin, James A. Ritter, Branko N. Popov, Ralph E. White

Faculty Publications

A mathematical model of an electrochemical capacitor with hydrous ruthenium oxide (RuO2·xH2O) electrodes including both double-layer and surface faradaic processes is developed to predict the behavior of the capacitor under conditions of galvanostatic charge and discharge. The effect of RuO2·xH2O particle size is studied and shows that the smaller the particles the better the performance because of the increased surface area per unit volume or mass. The model also predicts that the faradaic process increases significantly the energy per unit volume of the capacitor for power densities of …

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Development Of Carbon-Metal Oxide Supercapacitors From Sol-Gel Derived Carbon-Ruthenium Xerogels, Chuan Lin, James A. Ritter, Branko N. Popov Jan 1999

Development Of Carbon-Metal Oxide Supercapacitors From Sol-Gel Derived Carbon-Ruthenium Xerogels, Chuan Lin, James A. Ritter, Branko N. Popov

Faculty Publications

Sol-gel derived high surface area carbon-ruthenium xerogels were prepared from carbonized resorcinol-formaldehyde resins containing an electrochemically active form of ruthenium oxide. The electrochemical capacitance of these materials increased with an increase in the ruthenium content indicating the presence of pseudocapacitance associated with the ruthenium oxide undergoing reversible faradaic redox reactions. A specific capacitance of 256 F/g (single electrode) was obtained from a carbon xerogel containing 14 wt % Ru, which corresponded to more than 50% utilization of the ruthenium. The double layer accounted for 40% of this capacitance. This material was also electrochemically stable, showing no change in a cyclic …

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A Mathematical Model For Electroless Copper Deposition On Planar Substrates, M. Ramasubramanian, Branko N. Popov, Ralph E. White, K. S. Chen Jan 1999

A Mathematical Model For Electroless Copper Deposition On Planar Substrates, M. Ramasubramanian, Branko N. Popov, Ralph E. White, K. S. Chen

Faculty Publications

A mathematical model for the electroless deposition of copper on a planar electrode is presented and used to make time-dependent predictions on the various quantities in the system. The model takes into account mass transport by diffusion and migration, Butler-Volmer kinetics at the electrode surface, and mixed potential theory. A finite difference approach is used to solve the equations, and the resultant model is used to predict the concentration profiles, potential response, and plating rate as a function of time and concentration of various reactive components.

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Mathematical Modeling Of The Lithium Deposition Overcharge Reaction In Lithium‐Ion Batteries Using Carbon‐Based Negative Electrodes, Pankaj Arora, Marc Doyle, Ralph E. White Jan 1999

Mathematical Modeling Of The Lithium Deposition Overcharge Reaction In Lithium‐Ion Batteries Using Carbon‐Based Negative Electrodes, Pankaj Arora, Marc Doyle, Ralph E. White

Faculty Publications

No abstract provided.

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Influence Of Some Design Variables On The Thermal Behavior Of A Lithium‐Ion Cell, Gerardine G. Botte, Bradley A. Johnson, Ralph E. White Jan 1999

Influence Of Some Design Variables On The Thermal Behavior Of A Lithium‐Ion Cell, Gerardine G. Botte, Bradley A. Johnson, Ralph E. White

Faculty Publications

No abstract provided.

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A Simple Method For Determining Differential Diffusion Coefficients From Aqueous Electrolyte Diaphragm Cell Data At Temperatures Below 0°C, D. M. See, Ralph E. White Jan 1999

A Simple Method For Determining Differential Diffusion Coefficients From Aqueous Electrolyte Diaphragm Cell Data At Temperatures Below 0°C, D. M. See, Ralph E. White

Faculty Publications

No abstract provided.

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Methanol Fuel Cell Model: Anode, S. F. Baxter, V. S. Battaglia, Ralph E. White Jan 1999

Methanol Fuel Cell Model: Anode, S. F. Baxter, V. S. Battaglia, Ralph E. White

Faculty Publications

No abstract provided.

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Mathematical Modeling Of Electrochemical Capacitors, Venkat Srinivasan, John W. Weidner Jan 1999

Mathematical Modeling Of Electrochemical Capacitors, Venkat Srinivasan, John W. Weidner

Faculty Publications

Analytic solutions to the mathematical model of an electrochemical capacitor (EC) are used to study cell performance under two types of operating conditions: (i) constant current and (ii) electrochemical impedance spectroscopy. The analytic solution under constant-current operation is used to investigate the relative importance of ionic resistance in the separator, and ionic and electronic resistances in the porous electrode in the design and operation of an EC. Model results are presented that show the trade-off between energy and power density, as the physical properties of the cell components are varied (e.g., electrode thickness). The analytic solution …

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A Cloud-Removal Algorithm For Ssm/I Data, David G. Long, Douglas L. Daum, Quinn P. Remund Jan 1999

A Cloud-Removal Algorithm For Ssm/I Data, David G. Long, Douglas L. Daum, Quinn P. Remund

Faculty Publications

Microwave radiometers, while traditionally utilized in atmospheric and oceanic studies, can also be used in land surface applications. However, the problem of undesirable atmospheric effects caused by clouds and precipitation must be addressed. In this paper, temporal composite surface brightness images are generated from special sensor microwave/imager (SSM/I) data with the aid of new algorithms to eliminate small-scale distortion caused by clouds or precipitation. Mean, second-highest value, modified maximum average (MMA), and hybrid compositing algorithms are compared. The effectiveness of each algorithm is illustrated through simulation and real data distribution analysis. The results show that the second-highest value algorithm is …

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Spin-Up In A Tank Induced By A Rotating Bluff Body, R. Daniel Maynes, J. Klewicki, P. Mcmurty Jan 1999

Spin-Up In A Tank Induced By A Rotating Bluff Body, R. Daniel Maynes, J. Klewicki, P. Mcmurty

Faculty Publications

Spin-up of a turbulent flow in a cylindrical tank caused by a rotating bluff body has been investigated using flow visualization, fluid velocity measurements, and hydrodynamic torque measurements. During the spin-up process three distinct temporal regimes exist. These regimes are: (i) a build-up regime where the torque and the tangential velocity fluctuations in the close proximity of the body remain constant; (ii) a decay regime where these quantities decay with power-law relations; and (iii) a mean flow steady state where these values remain relatively constant. Experiments were conducted in two tanks differing in volume by a factor of 80 and …

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Micropolarizer Array For Infrared Imaging Polarimetry, M. W. Jones, Gregory P. Nordin, P. C. Deguzman, J. T. Meier Jan 1999

Micropolarizer Array For Infrared Imaging Polarimetry, M. W. Jones, Gregory P. Nordin, P. C. Deguzman, J. T. Meier

Faculty Publications

The design and fabrication of a micropolarizer array for imaging polarimetry is described for the 3–5-μm-wavelength region. Each micropolarizer consists of a 475-nm-period Mo wire grid in a 16 μm × 16 μm aperture. Interference lithography is used to generate the small grating features through an etch mask layer. Arrays of 256 × 256 micropolarizers at three distinct angular orientations have been fabricated that permit the measurement of the first three Stokes vector components in each pixel of an imaging polarimeter. An imaging system composed of a micropolarizer array integrated directly onto a focal plane array has been assembled, and …

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Development And Application Of A Correlation Of 13c Nmr Chemical Structural Analyses Of Coal Based On Elemental Composition And Volatile Matter Content, Dominic Genetti, Thomas H. Fletcher, Ronald J. Pugmire Jan 1999

Development And Application Of A Correlation Of 13c Nmr Chemical Structural Analyses Of Coal Based On Elemental Composition And Volatile Matter Content, Dominic Genetti, Thomas H. Fletcher, Ronald J. Pugmire

Faculty Publications

13C NMR spectroscopy has been shown to be an important tool in the characterization of coal structure. Important quantitative information about the carbon skeletal structure is obtained through 13C NMR spectral analysis of coal. Solid-state 13C NMR analysis techniques have progressed beyond the mere determination of aromaticity and can now describe features such as the number of aromatic carbons per cluster and the number of attachments per aromatic cluster. These 13C NMR data have been used to better understand the complicated structure of coal, to compare structural differences in coal, tar, and char, and to model …

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Modeling Nitrogen Release During Devolatilization On The Basis Of Chemical Structure Of Coal, Dominic Genetti, Thomas H. Fletcher Jan 1999

Modeling Nitrogen Release During Devolatilization On The Basis Of Chemical Structure Of Coal, Dominic Genetti, Thomas H. Fletcher

Faculty Publications

A model that predicts the amount and distribution between tar and light gas of nitrogen released during devolatilization has been developed and incorporated into the chemical percolation devolatilization (CPD) model. This work represents the first volatile nitrogen release model developed on the basis of 13C NMR measurements of coal structure. This work also represents the first volatile nitrogen release model evaluated by comparing model predictions with chemical structural features of the char (determined by 13C NMR spectral analyses). The model is limited to nitrogen release during primary pyrolysis, and assumes that all light-gas nitrogen is HCN. Model predictions …

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A Recursive Green's Function Method For Boundary Integral Analysis Of Inhomogeneous Domains, Jim D. Freeze, Michael A. Jensen Dec 1998

A Recursive Green's Function Method For Boundary Integral Analysis Of Inhomogeneous Domains, Jim D. Freeze, Michael A. Jensen

Faculty Publications

The recursive Green's function method (RGFM) for computation of fields scattered by two-dimensional (2-D) inhomogeneous dielectric bodies is presented. The algorithm efficiently constructs the Green's function for the inhomogeneous region by recursively combining known Green's functions from smaller subdomains. The fields on the scatterer surface are then computed using a boundary integral formulation. Proper implementation of the RGFM results in computational and storage complexities which scale as N1.5 and N, respectively, where N is the total number of discrete cells in a domain. Comparisons of results obtained using the RGFM with those computed from moment method and exact solutions show …

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The Evolution Of Probability Functions In An Inelasticly Deforming Two-Phase Medium, Brent L. Adams, H. Garmestani, S. Lin Dec 1998

The Evolution Of Probability Functions In An Inelasticly Deforming Two-Phase Medium, Brent L. Adams, H. Garmestani, S. Lin

Faculty Publications

A formulation is introduced here for the evolution of correlation functions in an inelastically deforming two phase medium. Probability functions play a major role in describing the statistical distribution of different phases in a heterogeneous medium in the development of statistical continuum theory. Proper formulation of statistical continuum model for inelastic deformation requires better understanding of the evolution of the corresponding probability functions. A two point probability function representation is used to approximate the statistical correlation functions. The evolution of these functions requires the information from higher order probability functions, in this case, a three point probability function. A decomposition …

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What Can Humor And Advertising Teach Us About Legal Drafting?, Dallin D. Oaks, Jeremy Lewis Dec 1998

What Can Humor And Advertising Teach Us About Legal Drafting?, Dallin D. Oaks, Jeremy Lewis

Faculty Publications

In his book Legal Drafting in a Nutshell, Haggard includes a useful chapter of nearly 50 pages in which he lists various lexical and structural elements and explains how these can lead to ambiguous writing. The kind of inventory approach that he presents is helpful and reveals that ambiguity doesn't just happen but often results from the careless use of identifiable structures or particular words.

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Successive Galerkin Approximation Algorithms For Nonlinear Optimal And Robust Control, Timothy Mclain, Randal W. Beard Nov 1998

Successive Galerkin Approximation Algorithms For Nonlinear Optimal And Robust Control, Timothy Mclain, Randal W. Beard

Faculty Publications

Nonlinear optimal control and nonlinear H infinity control are two of the most significant paradigms in nonlinear systems theory. Unfortunately, these problems require the solution of Hamilton-Jacobi equations, which are extremely difficult to solve in practice. To make matters worse, approximation techniques for these equations are inherently prone to the so-called 'curse of dimensionality'. While there have been many attempts to approximate these equations, solutions resulting in closed-loop control with well-defined stability and robustness have remained elusive. This paper describes a recent breakthrough in approximating the Hamilton-Jacobi-Bellman and Hamilton-Jacobi-Isaacs equations. Successive approximation and Galerkin approximation methods are combined to derive …

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Deriving Of Single Intensive Picosecond Optical Pulses From A High-Power Gain-Switched Laser Diode By Spectral Filtering, S. N. Vainshtein, Grigory Simin, J. T. Kostamovaara Oct 1998

Deriving Of Single Intensive Picosecond Optical Pulses From A High-Power Gain-Switched Laser Diode By Spectral Filtering, S. N. Vainshtein, Grigory Simin, J. T. Kostamovaara

Faculty Publications

Single 25 ps/16 W optical pulses were achieved by spectral filtering from a multiheterostructure gain-switched laser diode with its quasisteady-state modes suppressed by a factor of 103 as compared with the peak power. A significant transient spectrum broadening makes this possible provided that a very high dI/dt rate of the pumping current pulse is used. A simple numerical model is suggested which describes adequately both the spectral and transient features of the observed phenomenon. It follows from the model that single picosecond optical pulses can be obtained from any type of high power semiconductor laser.

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Chromium Oxides And Lithiated Chromium Oxides. Promising Cathode Materials For Secondary Lithium Batteries, Pankaj Arora, Dong Zhang, Branko N. Popov, Ralph E. White Sep 1998

Chromium Oxides And Lithiated Chromium Oxides. Promising Cathode Materials For Secondary Lithium Batteries, Pankaj Arora, Dong Zhang, Branko N. Popov, Ralph E. White

Faculty Publications

Chromiumoxides and lithiated chromium oxides were synthesized by thermal decompositionof chromium trioxide (CrO3) at high temperatures and oxygen pressures.Synthesis temperature and pressure markedly affect the performance of thesecathode materials. Higher pressures lead to a higher O/Cr ratioand fewer impurities in the final product. These materials arestable intercalation hosts for lithium, and exhibit a higher capacitythan any of the prominent positive electrodes used in secondarylithium batteries. m-CrOx has a capacity of 255 mAh/g, while m-LiCrOxhas a capacity of 210 mAh/g, during the first discharge. Theaverage voltage of these cells is 3.0 V vs. Li/Li …

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The Role Of Air Cargo In California's Goods Movement, H.-S. Jacob Tsao Sep 1998

The Role Of Air Cargo In California's Goods Movement, H.-S. Jacob Tsao

Faculty Publications

Caltrans began a systematic investigation into the role of air cargo in California’s goods movement, as part of the larger development effort for a statewide goods movement strategy, and funded a research project in 1997 for the Institute of Transportation Studies at U.C. Berkeley to (i) gain a broader understanding of the State’s air cargo industry and the role of air cargo in California’s goods movement, (ii) assess the importance of air cargo to the State’s economy, (iii) begin identification of issues hindering efficient air cargo movement in the State, and (iv) explore possible State roles for resolving the issues. …

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Nonlinear Optimal Control Design Of A Missile Autopilot, Tim Mclain, Randal W. Beard Aug 1998

Nonlinear Optimal Control Design Of A Missile Autopilot, Tim Mclain, Randal W. Beard

Faculty Publications

The application of a new nonlinear optimal control strategy to the design of missile autopilots is presented. The control approach described and demonstrated here is based upon the numerical solution of the Hamilton-Jacobi-Bellman equation by Successive Galerkin Approximation. Using this approach, feedback controllers are computed by an iterative application of a numerical Galerkin-type PDE solver. Simulation results demonstrating the application of this approach to the design of a missile autopilot are presented.

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Evaluation Of Personal Communications Dual-Antenna Handset Diversity Performance, Michael A. Jensen, Joseph S. Colburn, Yahya Rahmat-Samii, Gregory J. Pottie Aug 1998

Evaluation Of Personal Communications Dual-Antenna Handset Diversity Performance, Michael A. Jensen, Joseph S. Colburn, Yahya Rahmat-Samii, Gregory J. Pottie

Faculty Publications

In personal wireless communications systems, multipath propagation has a significant effect on system design and performance. Signal strength fading caused by destructive interference between multiple replicas of the signal of interest arriving at the receiver over different paths often is the limiting factor in system range/fidelity. Antenna diversity is one technique that can be used to help overcome multipath fading. This paper presents a description of experiments, data processing, and results used to evaluate the diversity performance of three candidate dual-antenna handset configurations: two side-mounted planar-inverted F antennas (PIFAs), a back-mounted PIFA with a top-mounted helix, a top-mounted PIFA, and …

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Influence Of Ash Deposit Chemistry And Structure On Physical And Transport Properties, Larry Lin Baxter 8507091 Jul 1998

Influence Of Ash Deposit Chemistry And Structure On Physical And Transport Properties, Larry Lin Baxter 8507091

Faculty Publications

Boiler ash deposits generated during combustion of coal, biomass, black liquor, and energetic materials affect both the net plant efficiency and operating strategy of essentially all boilers. Such deposits decrease convective and radiative heat exchange with boiler heat transfer surfaces. In many cases, even a small amount of ash on a surface decreases local heat transfer rates by factors of three or more. Apart from their impact on heat transfer, ash deposits in boilers represent potential operational problems and boiler maintenance issues, including plugging, tube wastage (erosion and corrosion), and structural damage. This report relates the chemistry and microstructural properties …

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Binary Multilevel Convolutional Codes With Unequal Error Protection Capabilities, Robert H. Morelos-Zaragoza, Hideki Imai Jul 1998

Binary Multilevel Convolutional Codes With Unequal Error Protection Capabilities, Robert H. Morelos-Zaragoza, Hideki Imai

Faculty Publications

Binary multilevel convolutional codes (CCs) with unequal error protection (UEP) capabilities are studied. These codes belong to the class of generalized concatenated (GC) codes. Binary CCs are used as outer codes. Binary linear block codes of short length, and selected subcodes in their two-way subcode partition chain, are used as inner codes. Multistage decodings are presented that use Viterbi decoders operating on trellises with similar structure to that of the constituent binary CCs. Simulation results of example binary two-level CC's are also reported.

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